Environmental concerns have caused industrial coating suppliers and users to reduce atmospheric pollution caused by volatile organic solvents that are emitted during the coating process. To address these concerns the coatings industry has formulated waterborne compositions that provide coatings with excellent physical and chemical properties. However, one problem with waterborne coating compositions particularly those used to form topcoats for automotive applications, is the formation of a defect-free film under a wide range of humidity conditions. Often the coatings are rougher than desired and have microscopic holes (“pinholing”), which adversely affect the physical properties of the coating. Controlling the humidity within narrow limits is often not possible in industrial applications without incurring considerable expense.
Therefore, it would be desirable to formulate an aqueous coating composition that can be deposited as a smooth coating, substantially free of defects under a variety of humidity conditions.